地电阻率观测中信噪比与观测精度  

STUDY ON SNR AND ACCURACY OF GEOELECTRICAL RESISTIVITY OBSERVATION

作　　者：张宇 王兰炜 张世中 张兴国 胡哲 ZHANG Yu;WANG Lan-wei;ZHANG Shi-zhong;ZHANG Xing-guo;HU Zhe(Institute of Geophysics,China Earthquake Administration,Beijing 100081,China;Institute of Earthquake Forecasting,China Earthquake Administration,Beijing 100036,China)

机构地区：[1]中国地震局地球物理研究所,北京100081 [2]中国地震局地震预测研究所,北京100036

出　　处：《地震地质》2024年第4期955-971,共17页Seismology and Geology

基　　金：中国地震局地震预测研究所基本科研业务专项(CEAIEF20240901)资助。

摘　　要：地电阻率观测方法在地震监测、预测研究中发挥了重要作用。地震监测、预测研究要求测量系统误差小且观测精度高,在测量系统性能指标满足测量最大允许误差的前提下,观测精度就取决于测量过程的信噪比,即观测场地的干扰情况。文中从理论上研究了地电阻率观测中信噪比和观测精度之间的关系,分析了地表和井下不同观测装置条件下信噪比的变化情况。当供电电流不变且主要受到均匀场的干扰影响时,减小极距可有效提高测量的信噪比。当地表装置的测量极距缩小为原来的1/3,或井下装置的测量极距缩小为原来的1/4时,信噪比可提高约20dB。以江宁台不同深度、极距观测结果为例,讨论了江宁台井下装置设计的合理性。文中研究结果可为今后地电阻率观测装置的设计和观测场地的选择提供参考。The geoelectrical resistivity observation method has played a significant role in earthquake monitoring and prediction research over the past 55 years.In the current geoelectrical resistivity observation system,the geoelectrical resistivity is indirectly measured by measuring the supply current and the artificial potential difference.To meet monitoring forecasting needs,the measurement system is required to have small measurement errors and high accuracy.When the observation instruments are applied to a seismic station,the primary influence is the site noise disturbance,the observation accuracy depends on the signal-to-noise ratio(SNR)of the measurement process.This study combines the measurement instruments and measurement methods used in the current network of geoelectrical resistivity observation stations and studies the relationship between observation accuracy and SNR in geoelectrical resistivity observation.Analyses the changes of SNR under the conditions of different observation configurations on the ground and borehole.Since SNR is related to the intensity of the interference and the artificial potential difference,also related to the supply current and the observation configuration.To improve the SNR under the interference conditions of a certain observing site,it can be done in 2 ways:to increase the supply current,and to reduce the electrode distance.Every doubling of the artificial potential difference requires a doubling of the power supply current and a 4-fold increase in power supply,with a corresponding increase in the SNR of 6 dB;if the SNR is increased by 20dB,it is equivalent to a 10-fold increase in supply current and a 100-fold increase in power supply,which is more difficult to achieve.When the power supply current is unchanged,and the main interference effect is a uniform field,the electrode distance reduction can effectively improve the SNR.If the ground electrode distance is reduced to 1/3 of the original,or the borehole electrode distance is reduced to 1/4 of the original,the SNR can be

关 键 词：地电阻率 信噪比 观测精度 极距 

分 类 号：P319.3[天文地球—固体地球物理学]